The present invention relates to a sputtering target suitable for formation of wiring of low resistance, an Al wiring film using the same, and electronic components comprising the Al wiring film such as semiconductor elements, liquid crystal display devices, surface acoustic wave devices or the like.
Recently, semiconductor industry typical in LSI is rapidly advancing. In semiconductor elements such as DRAMs, as higher integration and reliability advance, accuracy required for fine machining is also getting higher and higher. Further, for also sputtering targets being employed in forming wiring or the like, a more homogeneous metallic layer is demanded to form.
Among various kinds of metals for formation of the wiring, aluminum (Al) is attracting attention as formation material of low resistance wiring. Al is also expected as a wiring film being used as gate lines and signal lines of a TFT drive type liquid crystal display device (LCD). This is because as the size of LCD screen becomes larger, the wiring film of lower resistance is in demand. For instance, a large LCD of such as more than 10 inches necessitates the wiring of lower resistance of 10 xcexcxcexa9 cm or less.
Due to the Al wiring, the low resistance wiring can be realized. However, the Al film, due to heating at approximately 673K during heat treatment after CVD processing or wiring formation, generates protrusions called as hillock. This is because in the course of stress release of the Al film due to heating, Al atoms diffuse to generate the protrusions accompanying the diffusion of the Al atoms. Such protrusions, when generated in the Al wiring, adversely affect on the later process to cause problems.
Thereupon, it is tried to add a slight amount of metallic elements such as Cu, Si, Pd, Ti, Zr, Hf, Nd and Y to the Al wiring (Japanese Patent Laid-Open Publication No. HEI 5-335271). Specifically, these metallic elements are added to an Al target itself. Such metallic elements as mentioned above, forming an intermetallic compound with Al, function as trapping material of Al. Thereby, the aforementioned hillocks are suppressed from forming. In forming Al wiring for highly integrated semiconductor elements and large size LCDs, the Al alloy target that contains a slight amount of such a metallic element is in use.
Now, as higher integration, higher reliability and higher functionality of electronic devices such as semiconductor elements proceed, the structure thereof has become more complicated. As a result of this, a multi level interconnection structure has come to be adopted. Accordingly, further technological innovation is required in fine machining technology. In addition to the wiring, further improvement of reliability and longevity are in demand. For such purposes, sputtering films of high denseness and high orientation are in demand. Since such sputtering films are difficult to obtain by use of the existing general sputtering methods, new sputtering methods such as long throw sputtering or reflow sputtering are being adopted.
In sputtering by the general sputtering method, when segregation or internal defect exists in a target, dust or splash may occur due to an extraordinary electric discharge or the like. These cause defects during formation of DRAMs or TFT elements. There, investigation and elucidation of mechanism causing the dust or splash is in advance, and at the same time, development of preventive measure is also in progress. Some results are being obtained.
However, in the new sputtering methods such as the aforementioned long throw sputtering or reflow sputtering, higher power or higher temperature than ever is being advanced. Accordingly, thermal influence upon a target is becoming more than ever. In the long throw sputtering or reflow sputtering, the thermal influence on the target reaches up to for instance approximately 500xc2x0 C.
When forming, due to the long throw sputtering or reflow sputtering exposing the target to such severe conditions as mentioned above, an Al wiring film with an Al alloy target including a slight amount of metallic elements such as Cu, Si, Nd, Y or the like, lots of defect modes that have never been ascertained are found to occur. That is, there occurs lots of giant dust particles having a size such large as from 100 to 5000 xcexcm in the sputtered film to remarkably deteriorate yield of electronic devices such as DRAMs or TFT elements.
Further, in the long throw sputtering or reflow sputtering, there occur a problem that concavities or holes of relatively larger size occur in the sputtering films. These concavities or holes cause to deteriorate electromigration resistance or stress migration resistance. Accordingly, the yield of electronic devices such as DRAMs or TFT elements is deteriorated.
The existing dust preventive measure can not prevent the aforementioned giant dust particles or relatively large size concavities from occurring. Accordingly, sounder fine wiring networks are in demand to be formed by use of the long throw sputtering or reflow sputtering.
Further, in the Al wiring (Al alloy wiring) including a slight amount of the aforementioned metallic elements, due to the intermetallic compound formed between Al and an added element, Al can be suppressed from diffusing. However, there is a problem that a generated intermetallic compound can adversely affect on etching property of the Al wiring. That is, when dry etching such as CDE (Chemical Dry Etching) or RIE (Reactive Ion Etching), or wet etching is applied to the Al wiring film that contains an intermetallic compound, the intermetallic compound cause insoluble remains called as residue. This is largely detrimental in forming the fine wiring network.
From the above, in the Al target and Al wiring that are employed for forming the low resistance wiring, it is demanded to suppress the diffusion of Al due to the heating after film formation to prevent the hillock or the like from occurring. In addition to this, it is demanded for the residue also to be suppressed during etching.
An object of the present invention is to provide a sputtering target that enables to suppress new defect modes (giant dust particles or large concavities) from occurring. The new defect modes occur in particular, when the new sputtering methods such as long throw sputtering or reflow sputtering are employed. Further, the object includes, due to the use of such sputtering target, to provide Al wiring films that are excellent in hillock resistance and formation property of fine wiring network, and electronic components using such Al wiring films.
Further, another object of the present invention is to provide a sputtering target that can form with reproducibility Al wiring films of low resistance that are capable of preventing etching residue as well as hillock from occurring. Further, the object includes, by employing such sputtering target, to provide Al wiring films excellent in hillock resistance and formation property of fine wiring network, and electronic components employing such Al wiring films.
A first invention of the present application enables, through elucidation of reasons why to cause giant dust particles in the new sputtering method such as long throw sputtering or reflow sputtering, to suppress giant dust particles or the like from occurring. The first invention, by stipulating the degree of dispersion of added elements in a sputtering target with the mapping of EPMA (Electron Probe X-ray Microanalyzer) analysis, suppresses the giant dust particles from occurring.
A sputtering target of the first invention consists essentially of 0.1 to 50% by weight of at least one kind of element that forms an intermetallic compound with Al, and the balance of Al. Here, the element that forms the intermetallic compound is uniformly dispersed in the target texture, and, in a mapping of EPMA analysis, a portion of which count number of detection sensitivity of the element is 22 or more is less than 60% by area ratio in a measurement area of 20xc3x9720 xcexcm.
The other sputtering target of the first invention consists essentially of 0.1 to 50% by weight of at least one kind of element selected from a group consisting of Cu, Si, Sc, Y, La, Ce, Nd, Sm, Gd, Tb, Dy, Er, Pt, Ir, Ru, Pd, Ti, Zr, V, Nb, Ta, Fe, Ni, Cr, Mo, W, Mn, Tc, Re and B, and the balance of Al. Here, the element is uniformly dispersed in the target texture, and, in the mapping of EPMA analysis, a portion of which count number of detection sensitivity of the element is 22 or more is less than 60% by area ratio in a measurement area of 20xc3x9720 xcexcm.
The sputtering target of the first invention is further characterized in that, in the aforementioned mapping of EPMA analysis, a portion of which count number of the aforementioned element that forms the intermetallic compound or the element selected from the aforementioned group is 22 or more is less than 10% by area ratio in a measurement area of 200xc3x97200 xcexcm.
An Al wiring film of the first invention is characterized in that the Al wiring film is formed by use of the aforementioned sputtering target. The electronic component of the first invention comprises the aforementioned Al wiring film. As concrete examples of the electronic components, semiconductor elements, liquid crystal display devices, surface acoustic wave devices or the like can be cited.
In the new sputtering method such as long throw sputtering or reflow sputtering, higher power and higher temperature more than ever are in advance. Accordingly, thermal influence upon the target becomes more than ever (for example, approximately 500xc2x0 C.). Accordingly, the temperature of the sputtering target surface during sputtering becomes higher more than ever. Thereby, free energy of atoms constituting the target becomes large.
Accompanying such phenomena, the added element seeks for a stable area to precipitates at the grain boundary. Due to the precipitation of the added element, there occurs a large difference of the sputtering rate between the grain boundary and the interior of the grain to result in for only the interior portion of the grain to locally remain. Accordingly, on the surface of the target large unevenness is generated. When the sputtering is continued on in such a state, the rebounded sputtered particles begin sticking on the generated projections. Thereby, the projections become gigantic in the size thereof. Such projections fly off the sputtering target as a mass, thereby the giant dust particles stick on the substrate.
As mentioned above, due to an increase of thermal influence on the target, the added element precipitates at the grain boundary to generate the giant dust particle. The more non-uniform the initial state of dispersion is, that is the more segregated the added elements are, the more remarkable the precipitation of the added element becomes.
There, in the sputtering target of the first invention, the dispersion degree of the added element, in the mapping of EPMA analysis, is stipulated so that a portion where the count number of detection sensitivity of the added element is 22 or more is less than 60% by area ratio in a measurement area of 20xc3x9720 xcexcm. By satisfying such a state of dispersion, the precipitation of the added elements can be suppressed, thereby the giant dust particles can be suppressed from occurring.
According to the wiring film formed by use of the sputtering method such as long throw sputtering or reflow sputtering with the aforementioned first sputtering target, the giant dust particles can be suppressed from occurring. Accordingly, the product yield can be remarkably improved. In addition to this, based on the sputtering methods as described above, the Al wiring film of high denseness and high orientation can be provided.
A second invention of the present application, through elucidation of reasons why to cause the relatively large concavities or holes in the new sputtering method such as long throw sputtering or reflow sputtering, enables to suppress the giant dust particles and relatively large concavities and holes both based on the giant dust particles from occurring. In the second invention, by stipulating the dispersion degree of impurity elements such as Cr, Fe, C or the like in a target with the mapping of EPMA analysis, giant dust particles and relatively large concavities and holes both due to the giant dust particles are suppressed from occurring.
In a sputtering target in the second invention, a first mode is a sputtering target consisting essentially of 0.1 to 50% by weight of at least one kind of element that forms an intermetallic compound with Al, and the balance of Al. Cr contained in the aforementioned target is characterized in that, in the mapping of EPMA analysis, a portion of which count number of detection sensitivity of Cr is 33 or more is less than 60% by area ratio in a measurement area of 20xc3x9720 xcexcm.
A second mode is a sputtering target consisting essentially of 0.1 to 50% by weight of at least one kind of element that forms an intermetallic compound with Al, and the balance of Al. Fe contained in the target is characterized in that, in the mapping of EPMA analysis, a portion of which count number of detection sensitivity of Fe is 20 or more is less than 60% by area ratio in a measurement area of 20xc3x9720 xcexcm.
A sputtering target of a third mode is a sputtering target consisting essentially of 0.1 to 50% by weight of at least one kind of element that forms an intermetallic compound with Al, and the balance of Al. C contained in the aforementioned target is characterized in that, in the mapping of EPMA analysis, a portion of which count number of detection sensitivity of C is 55 or more is less than 60% by area ratio in a measurement area of 20xc3x9720 xcexcm.
The sputtering target of the second invention is further characterized in that, in each mapping of EPMA analysis of Cr, Fe and C as impurity element, a portion of which count number is more than the stipulated one for each element (the count numbers of Cr: 33, Fe: 20, and C: 55) is less than 10% by area ratio in a measurement area of 200xc3x97200 xcexcm.
An Al wiring film in the second invention is one that is formed by sputtering the aforementioned sputtering target. An electronic component in the second invention is one that comprises the aforementioned Al wiring film. As concrete examples of the electronic components, semiconductor elements, liquid crystal display devices, surface acoustic wave devices or the like can be cited.
In the new sputtering methods such as long throw sputtering or reflow sputtering method, as explained above, the temperature of the target surface becomes higher than ever during sputtering, thereby the free energy of atoms constituting the target becomes larger. Accompanying such phenomena, the impurity elements contained in the target, in particular Cr, Fe and C seek a stable area to precipitate at the grain boundary. Due to precipitation of these impurity elements, there occurs a large difference in the sputtering rates between the grain boundary and the inside of the grain. Thereby, only the interior of the grain locally remains on the target surface to form a large unevenness thereon.
In a state where the large unevenness is formed on the target surface, when the sputtering is further continued on, to the projections formed, sputtered particles rebound to stick to form giant projections. These giant projections fly off the target as a mass to stick on a substrate as giant dust particles. When such giant dust particles containing the impurity elements stick to the substrate, a mode of growth of the film changes only there from others to cause a difficulty in stacking the constituent atoms thereon. Thus, concavities and holes large relative to the sputtering film are formed.
As thermal influence on the target increases, the impurity elements such as Cr, Fe and C precipitate at the grain boundary to generate relatively large concavities and holes and the giant dust particles causing these. The less uniform the initial state of dispersion of the impurity element is, in other words, the more segregated the impurity in the target is, the more conspicuous the precipitation of the impurity element becomes.
There, in the sputtering target of the second invention, the degrees of dispersion of Cr, Fe and C, with the mappings of the EPMA analysis, are stipulated in the range as described above. By satisfying such dispersion states of Cr, Fe and C, these impurity elements can be suppressed from precipitating. As a result, the relatively large concavities and holes and the giant dust particles causing these can be suppressed from occurring.
With the second sputtering target such as described above, Al wiring films are formed by use of long throw sputtering or reflow sputtering. According to thus formed Al wiring films, the relatively large concavities or holes, being suppressed from occurring, can remarkably improve the product yield. In addition to this, due to the aforementioned sputtering method, the Al wiring films or the like of higher denseness and orientation can be provided.
The sputtering targets in the first and second inventions are not restricted in application to the long throw sputtering and reflow sputtering, but can be applied even in the existing general sputtering method. The same can be said with the Al wiring films of the first and second inventions.
In a third invention of the present application, occurrence of etching residue of an Al wiring film containing an element that forms an intermetallic compound and deterioration of finely etching property can be suppressed from occurring by incorporating Ar or Kr in the Al wiring film.
A sputtering target in a third invention consists essentially of at least one kind of element that forms an intermetallic compound with Al in the range of from 0.1 to 20% by weight, at least one kind of element selected from Ar and Kr by 5% by weight or less (not including 0% by weight), and the rest of Al.
Another sputtering target in the third invention consists essentially of at least one kind of element selected from Y, Sc, La, Ce, Nd, Sm, Gd, Tb, Dy, Er, Th, Si, Sr, Ti, Zr, V, Nb, Ta, Mn, Tc, Re, Cu and B in the range of from 0.1 to 20% by weight, at least one kind of element selected from Ar and Kr by 5% by weight or less (not including 0% by weight), and the rest of Al.
An Al wiring film in the third invention consists essentially of at least one kind of element that forms an intermetallic compound with Al in the range of from 0.1 to 20% by weight, at least one kind of element selected from Ar and Kr by 5% by weight or less (not including 0% by weight), and the rest of Al. Further, the Al wiring film is characterized in that it is formed by use of the aforementioned sputtering target of the third invention. An electronic component in the third invention is characterized in that the electronic component comprises the aforementioned Al wiring film. As the concrete examples of the electronic components, liquid crystal display devices, semiconductor elements, surface acoustic wave devices or the like can be cited.
In the third invention, to Al, together with an element that forms an intermetallic compound with Al such as Y, a slight amount of at least one kind of element selected from Ar and Kr is added. In the sputtering films obtained by use of such an Al target, there exist an intermetallic compound or an element that forms an intermetallic compound both poor in etching workability. However, Ar and Kr enhance their reactivity during etching. Further, Ar and Kr cause the intermetallic compound and the element themselves that forms an intermetallic compound that are poor in etching workability to finely and uniformly precipitate inside the grain of Al and at the grain boundary thereof.
Thus, Ar and Kr enhance the etching property (reactivity) of the intermetallic compound and the element itself that forms an intermetallic compound, and by finely and uniformly precipitating these, remarkably improve the etching property of the sputtered film, further can suppress the dust particles from occurring during sputtering. The added Ar or Kr does not adversely affect on suppression of diffusion of Al. Accordingly, the added element that forms an intermetallic compound can effectively prevent the hillock from occurring. Accordingly, the Al wiring films excellent in hillock resistance and in properties of forming fine wiring networks can be formed with reproducibility.